1. Field of the Invention
This invention relates to electronic locking systems and, more particularly, to an electronic lock system which depends on time-dependent user response codes which are prompted through audible (musical) tones.
2. Description of Prior Art
Presently, electronic locks operate passively, except to signal successful or unsuccessful operation. The operator must input information to the lock via electronic signals which are associated with a keypad, magnetic media or other code transmittal device. Other electronic locking devices are actuated by sophisticated scanning apparatus for producing unique electronic signals associated with an individual's body (fingerprint), voice or detectable forms of radiation. Such devices are inherently expensive and in many cases prone to error.
Most commonplace electronic locks are subject to fraudulent use if the electronic code (numerical or magnetic) is transferred to an unauthorized user. Conventional combinations are easy to transfer to others, and easy to forget. Physical keys (magnetic or otherwise) are usually inconvenient to carry or subject to loss or theft. Typical examples of these sorts of electronic lock-related devices, and previously mentioned devices, are found in the following patents: U.S. Pat. No. 4,286,305 issued to Pilat, U.S. Patent RE-29846 issued to Genest, U.S. Pat. No. 4,079,605 issued to Bartels, U.S. Pat. No. 3,821,704 issued to Sabsay, U.S. Pat. No. 4,031,434 issued to Perron, U.S. Pat. No. 3,184,937 issued to Sher, U.S. Patent RE-29341 issued to Peters, U.S. Pat. No. 3,639,906 issued to Tritsch, and U.S. Pat. No. 3,660,729 issued to James.
Electronic synthesis of music by both digital and analog means is well known. Digital methods are the most recent advancement and are discussed in U.S. Pat. No. 4,108,036 issued to Slaymaker and other sources. Analog electronic synthesis of sounds depends on oscillator circuits which are well known.
The device of this invention relies on digital logic circuitry which can take the form of discrete elements, or is equivalently synthesized with more complex components, such as computers which are suitably programmed. To keep track of digital information, necessary for the control and functions of the device, well-known methods for storage of digital information are utilized.